1. Field of the Invention
The present invention relates to a dehydration-compression system for dehydrating and compressing CO2 recovered from exhaust gas, and to a CO2 recovery system including the dehydration-compression system.
2. Description of Related Art
A dehydration-compression system (e.g., Japanese Unexamined Patent Application, Publication No. 2010-241630 (hereinafter referred to as “JP 2010-241630”)) recovers CO2 from exhaust gas discharged from an industrial facility, for example, a boiler or a gas turbine, and dehydrates/compresses the recovered CO2. For effective utilization of this dehydrated/compressed CO2, there are plans to inject the CO2 into an oilfield by the enhanced oil recovery (EOR) method, or store it in an aquifer aiming at combating global warming.
If moisture (H2O) remains in the compressed CO2, the moisture can condense during a transport process through a pipeline, etc. The condensed moisture causes corrosion of the pipeline and its ancillary equipment/machines, clogging of the pipeline due to generation of hydrate, and the like. For this reason, the moisture is removed from the CO2 by providing a dehydrating tower before the compressors, between the compressors, or after the compressors, which brings the CO2 and a liquid dehydration solvent such as triethylene glycol (TEG) or diethylene glycol (DEG) into contact with each other to absorb the moisture into the dehydration solvent. In the dehydration system of JP 2010-241630, TEG or the like after removing moisture is treated by combustion decomposition.
In another dehydration system proposed, a separation means for separating a dehydration solvent and moisture in a downstream stage of a dehydrating tower is installed, and the moisture is desorbed from the dehydration solvent having absorbed the moisture to thereby regenerate and recirculate the dehydration solvent to a dehydrating tower.
In the conventional dehydration systems, the moisture separated from a process fluid being dehydrated is commonly discharged to the outside of the system.
CO2 has affinity with a liquid dehydration solvent such as TEG and DEG. In the dehydration method using TEG or DEG, part of the CO2 is also absorbed into the dehydration solvent when CO2 and the dehydration solvent are brought into contact with each other. Thus, loss of the CO2 recovered by a CO2 recovery device occurs in the dehydration process.
Having been devised in view of the above problems, the present invention aims to provide a dehydration-compression system in which CO2 loss is suppressed, and a CO2 recovery system including the dehydration-compression system.